below the truth, the proportion has seemed to be nearly accurate. He conceives, that the weight of the blood is to that of the whole body as 1 to 5. Accordingly, an individual weighing one hundred and fifty pounds, will have about thirty pounds of blood; one of two hundred pounds, forty; and so on. Of this, one-third is supposed to be contained in the arteries, and two-thirds in the veins. The estimate of Haller' is, perhaps, near the truth; the arterial blood being, he conceives, to the venous, as 4 to 9. Were we, therefore, to assume that the whole quantity of the blood is thirty pounds in a man weighing one hundred and fifty pounds, which is perhaps allowing too much,--nine pounds, at least, may be contained in the arteries, and the remainder in the veins. An ingenious plan, proposed by Valentin2 for estimating the quantity of blood in the body, affords an approximation to the truth, and is confirmatory of the estimate made from other data. Having weighed an animal, and determined the proportion of solid matter in a portion of its blood, he injects into its vessels a given quantity of distilled water, which soon becomes mixed with the blood. He then takes away a fresh portion of blood, and ascertains the proportion of solid matter in it. The relation between the amount of solid matter in the blood first taken, and that in the blood diluted with the given quantity of water, enables him to calculate the quantity of blood in the body of the animal. The following question and solution are given, in order to show, how the quantity of blood may be estimated in the manner proposed by Valentin. A portion of blood, (=1190 grains,) drawn from a dog, yielded 24.54 per cent. of solid matter. After injecting 10,905 grains of water into the bloodvessels, a portion of blood drawn yielded 21.86 (or, by another trial, 21.89) per cent. of solid matter. What was the amount of blood in the body at the commencement of the experiment? Let z be the amount of blood after the first experiment. Then, since it contained 24.54 per cent. of solid residue, the amount of solid matter in it was ·2454 x. After injecting the water the whole amount of the diluted blood was x + 10905; and, (by the experiment,) the solid matter which it contained was =2186 (x + 10905). But the solid matter was of the same amount in both cases. Therefore we have, or, or, 2454x2186 (x+10905) Add for the blood first drawn And we get 90135 grs. the weight of blood in the body, at the commencement of the experi ment. The ratio 21.89 per cent. gives And the mean of the two is 1 Op. cit., lib. v. sect. 1, § 3. 91269 grs. 2 Lehrbuch der Physiologie des Menschen, i. 490, Braunschweig, 1844. In this manner, Valentin found the ratio of blood to the weight of the body to be in the dog as 1 to 4.36 in the male sex, and 1 to 4.93 in the female; and adapting these proportions to M. Quetelet's table of the weight of the human subject at different ages, he infers, that the mean quantity of blood in the male adult, at the time when the weight of the body may be presumed to be greatest, namely, at 30 years, should be about 341 pounds; and that of the female at 50, when the weight is generally greatest, at about 26 pounds. It is difficult, however, to believe, that there is not some fallacy in these calculations. The proportion of blood to the rest of the body, judging from the quantity that has usually flowed from animals bled to death, and the apparent quantity remaining in the vessels, seems to be excessive; and such is the view of Professor Blake of Saint Louis. In a recent letter to the author, he refers to experiments instituted by him, which consisted in injecting a weighed quantity of sulphate of alumina into the veins, and analyzing a weighed portion of the blood. As the salt had time to be well mixed with the blood before the animal died, such an analysis, he conceived, would enable the whole quantity of blood with which the salt had been mixed to be determined. The only error which—it appeared to him-might arise would be from a portion of the salt having combined with some of the tissues, or having been rapidly excreted, which could only affect the result in one direction, viz. in furnishing a greater quantity of blood than really exists. The results led Dr. Blake to infer, that there was no such source of error, as he found by this method, that the weight of blood in the body of a dog does not amount to more than between one-eighth or one-ninth part of the weight of the animal, a ratio much lower-as has been shown-than is generally conceived. "That this, however, is nearer the truth is probable from the consideration of the velocity of the circulation and the capacity of the heart, as, on the generally received opinion of the quantity of the blood, it is difficult to imagine how it can circulate so rapidly." This estimate would give the quantity of blood in a man weighing 150 pounds from 163 lbs. to 183-not very far from the recent estimate of Günther-which is from 15 to 20 pounds. "1 The blood strongly resembles the chyle in properties; the great difference consisting in the colour. The venous blood, the chyle, and the - lymph become equally converted into the same fluid-arterial bloodin the lungs: both the chyle and lymph may, indeed, be regarded as rudimental blood. Venous blood, which chiefly concerns us at present, is contained in all the veins, in the right side of the heart, and in the pulmonary artery; organs which constitute the apparatus of venous circulation. As drawn from the arm its appearance is familiar to every one. At first, it seems to be entirely homogeneous; but, after resting for some time, separates into different portions. The colour of venous blood is much darker than that of arterial; so dark, indeed, as to have led to the epithet black blood applied to it. Its smell is faint and peculiar; by 1 Medical Examiner, August, 1849, p. 459. 2 Lehrbuch der Physiologie des Menschen, ii. Band. 1 Abtheilung. s. 122, Leipzig, 1848. some compared to a fragrant garlic odour, but sui generis; its taste is slightly saline, and also peculiar. It is viscid to the touch; coagulable; and its temperature has been estimated at 96° Fahrenheit; simply, we believe, on the authority of the inventor of the thermometric scale, who marked 96° as blood heat. This is too low by at least three or four degrees. Rudolphi,' and the German writers in general, estimate it at 29° of Réaumur, or "from 98° to 100° of Fahrenheit;" whilst, by the French writers in general, its mean temperature is stated at 31° of Réaumur, or 102° of Fahrenheit; M. Magendie, who is usually very accurate, fixes the temperature of venous blood at 31° of Réaumur, or 102° of Fahrenheit; and that of arterial blood at 32° of Réaumur, or 104° of Fahrenheit. 100° may perhaps be taken as the average. This was the natural temperature of the stomach in the case related by Dr. Beaumont, which has been so often referred to in these pages. In many animals, the temperature is considerably higher. In the sheep it is 102° or 103°; but it is most elevated in birds. In the duck, it is 107°. On this subject, however, further information will be given under the head of CALORIFICATION. 3 2 The specific gravity of blood is differently estimated by different observers. Hence it is probable, that it varies in individuals, and in the same individual at different periods. Compared with water, the mean has been estimated, by some, to be as 1-0527; by others, as 1-0800, to 1.0000. It is stated, however, to have been found as high as 1.126; and, in disease, as low as 1.022. It has, moreover, been conceived, that the effect of disease is, invariably, to make it lighter; and that the more healthy the individual, the greater is its specific gravity; but our information on this point is vague. That it is not always the same in health, is proved by the discrepancy of observers. Boyle estimated it to be 1.041; Martine, 1.045; Jurin, 1·054; Muschenbroek, 1.056; Denis, 1.059; Sénac, 1.082; Berzelius, from 1.052 to 1.126; J. Müller, from 1.0527 to 1·0570; Mandl, from 1.050 to 1-059; and Dr. G. O. Rees, from 1.057 to 1.060. In a large number of experiments made upon the blood of man, the ox, and horse, M. Simon found it to be between 1.051 and 1.058. The average was 1.042, which, he says, corresponds very nearly with the statement of Berzelius. The average may perhaps be 1.050. Nasse says 1.055; Zimmerman, 1.056. A part of the discrepancy may be owing to the specific gravity not having been always taken at the same temperature. Dr. B. Babington found experimentally, that four degrees of temperature corresponded with a difference of 001 of specific weight; consequently, if one author states the specific gravity of blood at about its circulating temperature-say 98° of Fahr.-while another states it at 60° Fahr.-the usual standard-the former will make it 0095 lighter than the latter. The blood of man is thicker, and at least one-thousandth heavier than that of woman. 1 Grundriss der Physiologie, i. 143, Berlin, 1821. 3 Experiments, &c., on the Gastric Juice, &c., p. 274, Plattsburg, 1833. 4 Animal Chemistry, Sydenham edition, p. 100, Lond., 1845. When blood is examined with a microscope of high magnifying power, it appears to be composed of numerous, minute, red particles or corpuscles,-commonly called red globules, blood corpuscles, and blood disks,-suspended in the serum. These corpuscles have a different shape and dimension, according to the nature of the animal. In the mammalia, they are circular; and, in birds and cold-blooded animals, elliptical. In all animals, they are affirmed, by some observers, to be flattened, and marked in the centre with a luminous point, of a shape analogous to the general shape of the corpuscle. Professor Giacomoni,1 of Padua, has, however, affirmed, that the red corpuscles swimming in serum,-which have been described, by so many writers, in the circulating fluid,-exist only in the imagination. As in every case that rests on microscopic observation, the greatest discrepancy prevails, not only as regards the shape, but the size of the corpuscles. These were first noticed by Malpighi; and afterwards more minutely examined by Leeuenhoek, who at first described them correctly enough in general terms; but subsequently became hypothetical; and advanced the fantasy, that the red corpuscles are composed of a series of globular bodies, descending in regular gradations; each of the red corpuscles being com Fig. 291. posed of six particles of serum; a particle of serum of six particles of lymph, &c. Totally devoid of foundation as the whole notion was, it was believed for a considerable period, even until the time when Haller wrote. Mr. Hewson3 described the corpuscles as consisting of a solid centre, surrounded by a vesicle, filled with a fluid; and to be "as flat as a guinea." Mr. Hunter, on the other hand, did not regard them as Represented at a, as they are seen when solid bodies, but as liquids possessing Red Corpuscles of Human Blood. Magnified 400 diameters. (Donné.) rather beyond the focus of the microscope; a central attraction that determines and at 6 as they appear when within the focus. their shape. Della Torres supposed them to be a kind of disk or ring, pierced in the centre; whilst Dr. Monro conceived them to be circular, flattened bodies, like coins, with a dark spot in the centre, which he thought was not owing to a perforation, as Della Torre had imagined, but to a depression. Cavallo, again, conceived, that all these appearances are deceptive, depending upon the peculiar modification of the rays of light, as affected by the form of the particle; and he concluded, that they are simple spheres. Amici found them of two kinds; both with angular margins; but, in the one, the centre was depressed on both sides; whilst, in the other, it was elevated. The observations of Dr. Encyclogr. des Sciences Médicales, Avril, 1840, p. 529. 2 Opera, Lond., 1687. 3 Experimental Inquiries, part. iii. p. 16, Lond., 1777, or Hewson's Works, by Gulliver, Sydenham Society's edit., p. 215, Lond., 1846. On the Blood, &c., by Palmer, Amer. edit., p. 63, Philad., 1840. 5 Philos. Trans. for 1765, p. 252. 6 An Essay on the Medicinal Properties of Factitious Air, &c., p. 237, Lond., 1798. 2 Young,' of Sir Everard Home and Mr. Bauer, and of MM. Prévost and Dumas,3 accord chiefly with those of Mr. Hewson. All these gentlemen consider the red corpuscles to be composed of a central globule, which is transparent and whitish; and of a red envelope, which is less transparent. Dr. Hodgkin and Mr. Lister have denied that they are spherical, and consist of a central nucleus enclosed in a vesicle. They affirm, on the authority of a microscope, which, on comparison, was found equal to a celebrated one, taken a Fig. 292. 3 Blood Corpuscles of Rana Esculenta. few years ago to Great Britain by Professor Amici,' that the particles of human blood appear to consist of circular, flattened, transparent cakes, their thickness being about th part of their diameter. These, when seen singly, appear to be nearly or quite colourless. Their edges are rounded, and being the thickest part, occasion a depression in the middle, which exists on both surfaces. The view of these gentlemen, consequently, appears to resemble that of Dr. Monro. Mr. Gulliver, however, thinks that the ratio of 1 to 45, given by Dr. Hodgkin and Mr. Lister, must be a misprint. From measurements of the thickness, at the circumference of the corpuscles of several mammalia, he found it to be generally one-third and one-fourth the diameter: the average thickness of the human blood corpuscle he estimates at 12th of an English inch, and the diameter at 200th. 1, 1, 1, 2. Blood corpuscles. 2. Seen edgewise. 3. Lymph corpuscle. 4. Altered by dilute acetic acid. (Wagner.) Amidst this discordance, it is difficult to know which view to adopt. The belief in their consisting of circular, flattened, transparent bodies, with a depression in the centre, and of an external envelope and a central nucleus, the former of which is red and gives colour to the blood, has had, perhaps, the greatest weight of authority in its favour. The nucleus has appeared to be devoid of colour, and to be independent of the envelope; as, when the latter is destroyed, the central portion preserves its original shape. The nucleus is much smaller than the envelope, being, according to Dr. Young, only about one-third the length, and one-half the breadth of the entire corpuscle. According to Sir Everard Home," the corpuscles, enveloped in the colouring matter, are 1th part of an inch in diameter, requiring 2,890,000 to a square inch; but deprived of their colouring matter they appear to be th part of an inch in diameter, requiring 4,000,000 corpuscles to a square inch. From these measurements, the corpuscles, when devoid of colouring matter, are not quite one-fifth smaller. The views of MM. Prévost and Dumas, who have investigated the subject with extreme care and 1 Introduct. to Med. Literature, p. 545. 2 1 2 Philosoph. Transact. for 1811-1818; and Lectures on Comp. Anat., iii. 4, Lond., 1823. Annales de Chimie, &c., xxiii. 50, 90; and Journal of Science and Arts, xvi. 115. Philosoph. Magazine and Annals of Philosophy, ii. 130, Lond., 1827. Edinb. Medical and Surgical Journal, xvi. 120. Hewson's Works, Sydenham Society's edit., note to page 215, Lond., 1846. 7 Lectures on Comparative Anatomy, iii. 4, and v. 100, Lond., 1828. |